1. Field of the Invention
The present invention relates to the field of imaging, and specifically to an imaging arrangement and barcode imager for imaging an optical code or target at a plurality of focal planes.
2. Description of the Related Art
CCD or CMOS-based imaging devices, such as conventional barcode imagers, generally have limited working ranges on the order of 5–61 cm (˜2–24 inches). Furthermore, the aiming axis is often misaligned with the imaging axis of the imaging device. In many cases, the imaging device is designed to be handheld or at least moveable within a given area, thus compensating, somewhat, for the limited working range and skewed axis. However, the operator is still required to position the imaging device within the proper range and angle to produce an adequately sharp, i.e., substantially focused image. This may require a trial and error approach on the part of the operator in order to obtain the proper distance and angle from the target to be imaged.
In applications where the imaging device is kept stationary (e.g., fixed mount applications), such as in an assembly line where the imaging device is generally fixed for imaging barcode symbols on objects being moved along the assembly line, the conventional working range (i.e., 5–61 cm) is generally acceptable. In many applications where an increased working range is necessary, expensive and complex imaging arrangements having state-of-the-art automatic focus systems, such as zoom capabilities, are generally incorporated within or used in conjunction with barcode imagers to increase their working range. However, such imaging arrangements, besides being expensive, generally require constant maintenance. Therefore, when an application calls for imaging and decoding one-dimensional and two-dimensional barcode symbols, these imaging arrangements do not compete well in the marketplace against laser-based barcode readers which have comparable or even greater working ranges, and generally are less expensive.